Acetal polymers represent an important class of engineering resins due to numerous favorable physical properties. For this reason, acetal polymers have a wide range of commercial applications, for example, as parts for automobiles, as plumbing components and a variety of household and personal products.
It is oftentimes desireable to modify one or more of the inherently advantageous physical properties of acetal polymers so as to meet the needs of specific end-use applications. Normally, to achieve such modified properties, acetal polymers are blended with a variety of other resins and/or ingredients (e.g., impact modifying agents, flame retardants, light and heat stabilizers, fillers, and the like). Usually the blending of acetal polymers is not without its own problems due principally to the highly crystalline nature of acetal polymers which is evident in a low level of compatibility with other polymers.
Grafting of a different resin and/or a specific chemical moiety onto a polyacetal backbone would present an attractive alternative to blending so as to achieve a block copolymer having the desired modified physical and/or chemical properties. However, with acetal polymers, grafting is usually not possible due to the low level of polyacetal end group functionality--that is, since each acetal copolymer molecule carries a maximum of two functional groups, e.g., hydroxyl end groups.
According to the present invention, however, a novel class of polyacetal terpolymers is provided which retain the beneficial physical and chemical properties of conventional acetal polymers, while yet also providing greatly increased functionality. Therefore, the acetal terpolymers of this invention may be reacted with other resins and/or chemical moieties so as to, for example, permit a variety of acetal polymers to be synthesized having chemically bound (i.e., not merely blended) modifying agents.
Broadly, the terpolymers of the present invention are obtained by the cationic copolymerization of trioxane with a mixture of .alpha.,.alpha.- and .alpha.,.beta.-isomers of glycerol formal or their ester functionalized derivatives. The resulting terpolymer will therefore exhibit side chain funtionality (i.e., in the form of pendant hydroxyl or ester functional groups) so as to enable synthesis of, for example, block polymers comprised of the acetal terpolymer of this invention and other specific polymers to achieve desired chemical and/or physical properties.
These, as well as other aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments.